Vehicle security systems are widely used to deter vehicle theft, prevent theft of valuables from a vehicle, deter vandalism, and to protect vehicle owners and occupants. A typical automobile security system, for example, includes a central processor or controller connected to a plurality of vehicle sensors. The sensors, for example, may detect opening of the trunk, hood, doors, windows, and also movement of the vehicle or within the vehicle. Ultrasonic and microwave motion detectors, vibration sensors, sound discriminators, differential pressure sensors, and switches may also used as sensors. In addition, radar sensors may be used to monitor the area proximate the vehicle. The controller also typically operates to give an alarm indication in the event of triggering of a vehicle sensor. The alarm indication may typically be a flashing of the lights and/or the sounding of the vehicle horn or a siren. In addition, the vehicle fuel supply and/or ignition power may be selectively disabled based upon an alarm condition.
A typical security system also includes a receiver associated with the controller that cooperates with one or more remote transmitters typically carried by the user as disclosed, for example, in U.S. Pat. No. 4,383,242 to Sassover et al. The remote transmitter may be used to arm and disarm the controller in the vehicle or provide other remote control features from a predetermined range outside the vehicle.
As disclosed in U.S. Pat. No. 5,049,867 to Stouffer and U.S. Pat. No. 5,146,215 to Drori, the controller may include features to store and compare unique codes associated with a plurality of remote transmitters, each remote transmitter having its own unique code initially programmed therein. Transmitter codes may be added or deleted from the controller corresponding to the number of remote transmitters desired by the user.
In addition, a typical security system includes a valet switch, for example, to permit the system to enter the so-called valet mode, wherein the alarm functions are disabled. The valet mode permits authorized use of the vehicle by a technician or valet without concern for the vehicle alarm inadvertently being triggered. Typically, the valet switch is positioned away from plain view in the vehicle. A vehicle security system sold under the mark VIPER included the ability to enter the valet mode via a remote transmitter. The remote activation disabled security features of the system, but left convenience features still operable.
Many other features may be incorporated into a vehicle security system. For example, as disclosed in U.S. Pat. No. 4,887,064 to Drori et al. the controller may include self-diagnostics. In the event of a sensor failure, the controller will bypass the sensor, permit arming of the system, and the bypassed sensor will not cause activation of the alarm. Unfortunately, a reduced level of security is then provided. A flashing LED, sound signal, or voice message may be used to give an indication that the alarm has been triggered. The audible alarm signal may be selected by the user. An alarm may also be given when power is restored after having been disconnected, as when a thief disconnects the power to avoid the security system and attempts to then start the vehicle. An LED is mounted on the vehicle instrument panel or dashboard so that the controller may visually communicate with the user. A keypad may also be mounted within the vehicle to permit the user to program certain features of the security system. Control functions may also be implemented by the security system including: accessory, pulsed alarm, hood release, ignition cutoff, door lock and unlock.
A vehicle security system may also include a passive arming feature wherein the status of all trigger inputs is monitored in several protection zones. These zones may include the passenger compartment, the engine compartment, the trunk, and additional sensor zones such as for motion, impact, and or glass breakage. When the ignition key is turned off, the system begins the passive arming process. If all zones are secure, normal arming occurs after expiration of an exit delay. If any zone becomes active during the exit delay, the process begins again. U.S. Pat. No. 4,754,255 to Sanders et al. discloses a variation of passive arming wherein any unsecured zone is monitored when the ignition key is turned off.
The alarm of a typical vehicle security system will time out after the alarm has been activated, regardless of whether the owner has returned to reset the system. Unfortunately, if a sensor is defective, the security system will repeatedly sound the alarm until the battery of the vehicle is exhausted. U.S. Pat. No. 5,157,375 to Drori discloses a vehicle security system that attempts to reduce noise pollution and reduce battery drain caused by an unattended security system with a defective sensor having repeating alarm cycles. In particular, the patent discloses that after a predetermined number of alarm cycles, such as ten alarm cycles from one sensor, the sensor is bypassed until the system is reset. The patent also discloses an optional feature wherein the first time a sensor is triggered, an alarm occurs. However, once a sensor has tripped an alarm, then subsequently an active sensor will cause an alarm only if another trigger is also active.
U.S. Pat. No. 4,922,224 discloses that upon triggering of a first sensor a first alert signal is provided. Thereafter, a more pronounced second alert signal is provided if another trigger is received while the first sensor is also activated.
U.S. Pat. No. 4,754,255 to Sanders, et al. discloses that if a zone is tripped it will cause the alarm to sound for a specific time, such as eight minutes. Thereafter the zone is ignored and the other zones are continuously monitored. If the tripped alarm subsequently becomes secure, it is again monitored and may cause an alarm. For short duration output sensors, such as a shock sensor, once the cumulative tripped time exceeds eight minutes, the sensor zone will be ignored until the owner disarms the system.